| Aditus to mastoid antrum | |
| Latin: | aditus ad antrum mastoideum |
The aditus to mastoid antrum (otomastoid foramen) is a large, irregular opening[1] upon the posterior wall of the tympanic cavity by which the mastoid antrum (situated posteriorly) communicates with the epitympanic recess of the tympanic cavity (situated anteriorly).[2] The walls of the antrum are lined by mucosa which is continuous with that lining the mastoid cells and tympanic cavity.[3]
The medial wall of the aditus features a ridge created by the underlying facial canal, and a bulge created by the underlying ampulla of the lateral semicircular canal. The short limb of incus is lodged in a shallow fossa upon the posterior wall of the tympanic cavity just inferior to the aditus. The pyramidal eminence is situated inferior to the aditus.